What is a Soil Pipe?

what is a soil pipe? picture of black soil pipe against house

What is a Soil Pipe?

A soil pipe (sometimes known as a vent pipe, stack pipe and waste vent pipe) is the pipe that would usually connect to your pan connector that attaches to your toilet and would typically run externally down the side of the house or property and connect into the underground sewer system. Soil pipes will also have boss connections for attaching waste pipe to dispose of waste water from the bath, sink, and appliances of a property. The soil pipe would then run upwards to just above roof gutter level where a vent will be installed to allow air flow to stop a vacuum and allow the waste water to flow correctly. Occasionally the soil pipe will run internally, and in this case an air admittance valve will be required to allow air flow into the system while stopping air (and thus smell) from being released into the property.

Soil pipes are most commonly made from plastic (PVC) as this makes them easy to work with, light weight and cheaper than their cast-iron alternatives which are heavy, expensive and difficult to manage.

How does Soil Pipe work?

As mentioned above the soil pipe is installed to transport waste and sewage from upper floor toilets, baths and sinks and appliances into the underground drainage system. However, the vents allow smells and odours from the waste and drainage system to be released into the atmosphere. Placing the outlet at roof level means the odours are dispersed of somewhere where it won’t be smelt. The vents also help the process of aerobic sewage digestion by allowing air flow and oxygen into the system.

What size Soil Pipe do I need?

Soil pipes generally come in sizes from 3 inch to 6 inch, these are 75mm, 110mm and 160mm in metric, and are supplied in 3m or 4m lengths with the best seller being the 110mm x3m Soil Pipe. The size you need will depend upon the outlets and inlets you need to connect to, and the amount of waste water that will be transported through the pipe. A standard home will usually use a 110mm (or 4 inch) soil pipe, which would connect into a standard pan connector, and into a standard 110mm underground drainage system.

What colour Soil Pipes are available?

The most common colour is black, followed by grey and then white. At Easymerchant we stock black and grey, and can source white when necessary. There are other decorative colours available such as green, cream, beige, blue etc – however demand is low and lead times are high. If you’re after one of these decorative colours then feel free to call us and we’ll source them for you.

How do we join Soil Pipes together?

The two most common ways of joining soil pipes together are push fit joints, which are joined together by pushing the pipes together where a rubber seal prevents leakage. Or by solvent weld, where a solvent glue will be used to glue the pipes together creating a permanent seal. We’ve written a guide detailing how to join various different types of pipe together here.

We hope this answers some of the common questions we get here at Easymerchant, thanks for reading!

One thought on “What is a Soil Pipe?

  1. Sarah says:

    A vital pipe that not a lot is known about, especially by homeowners. This is a fab explanation, quick and simple to understand. Hopefully this will give plumbers a better way to describe exactly what they are doing to a house, which increases the ease of contact and rapport between the homeowner and the plumber – always a bonus.

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